1. Field
The present invention relates to a light emitting diode (LED) driving apparatus and driving method for continuously driving an LED, and more particularly, to an LED driving apparatus and driving method for continuously driving an LED capable of compensating for a light output of an LED lighting using an energy chargeable and dischargeable element and/or circuit.
2. Discussion of the Background
A light emitting diode (LED) is generally driven in a direct current driving mode. In a case of the direct current driving mode, there are problems that an alternating current-to-direct current (AC-DC) converter such as a switching mode power supply (SMPS), or the like is necessarily required, the power converter increases cost of manufacturing a lighting fixture, makes miniaturization of the lighting fixture difficult, degrades energy efficiency of the lighting fixture, and shortens a lifespan of the lighting fixture due to a short lifespan of the power converter.
In order to solve the problems of the direct current driving mode described above, an alternating current driving mode of the LED has been proposed (Korean Patent Laid-Open Publication No. 10-2012-0032509, etc.). However, a circuit according to the above-mentioned technology has a problem that a flicker phenomenon in which a user recognizes a flicker of a lighting due to a long non-emitting interval of the LED occurs as well as a problem that a power factor is degraded due to a non-match between an input voltage and a current output from the LED.
In order to solve the problems of the alternating current driving mode of the LED as described above, a sequential driving mode of an alternating current LED has been proposed (Korean Patent Laid-Open Publication No. 10-2012-0041093, etc.). According to the sequential driving mode of the alternating current LED described above, in a situation in which an input voltage is increased over time, a first LED first begins to emit light at Vf1, a second LED is connected in series to the first LED at Vf2 which is a voltage higher than Vf1, such that the second LED begins to emit light, and a third LED is connected in series to the second LED and the first LED at Vf3 which is a voltage higher than Vf2, such that the third LED begins to emit light. In addition, in a situation in which the input voltage is decreased over time, the third LED first stops the emitting of light at Vf3, the second LED stops the emitting of light at Vf2, and the first LED finally stops the emitting of light at Vf1, such that an LED driving current is designed so as to approximate the input voltage. In according to the sequential driving mode of the alternating current LED, since the LED driving current is converged in a form similar to the alternating current input voltage, the power factor may be improved. However, there are problems that the flicker phenomenon still occurs in the non-emitting interval in which the input voltage does not reach Vf1 and light characteristics of the lighting fixture are not uniform because emitting times for each light emitting module of the LED are different from each other.
Meanwhile, in order to solve the problems of the sequential driving mode of the alternating current LED, various technologies for removing the non-emitting interval using a smooth capacitor, a power factor correction circuit, and the like have been proposed (Korean Patent Laid-Open Publication No. 10-2010-0107196). However, according to the above-mentioned technologies, there is a problem that total harmonic distortion (THD) is rather deteriorated due to element characteristics in which the current is sharply increased at a timing in which the smooth capacitor begins to charge. In addition, there is a problem that high capacitance is required because the smooth capacitor should maintain a voltage of at least Vf3 or more in order to drive all LEDs in the non-emitting interval. In addition, due to the above-mentioned problems, there is a problem that cost of the smooth capacitor is increased and it is difficult to miniaturize the LED lighting fixture.